1 Kings 12:33

On the fifteenth day of the eighth month, a month of his own choosing, Jeroboam offered sacrifices on the altar he had set up in Bethel. So he ordained a feast for the Israelites, offered sacrifices on the altar, and burned incense.

So he offered upon the altar which he had made in Beth-el the fifteenth day of the eighth month, even in the month which he had devised of his own heart; and ordained a feast unto the children of Israel: and he offered upon the altar, and burnt incense.